Defensive publication



DEFENSIVE PUBLICATION UNITED STATES PATENT OFFICE Published at the request of the applicant or owner in accordance with the Notice of Apr. 11, 1968, 849 0.G. 1221. Identification is by serial number of the application and the heading indicates the number of pages of specification, including claims, and of sheets of drawing contained in the application as originally filed. The file of this application is available to the public for inspection; reproduction may be purchased for 130 cents per sheet.

Applications published under the Defensive Publication Program have not been examined as to the merits of alleged Invention. The Patent Oflice makes no assertion as to the novelty of the disclosed subject matter.

PUBLISHED MAY 6, 1969 748 659 POLYCARBODIIMIDES FOR IMPROVING AGING RESISTANCE 0F POLYESTER FIBER IN SULFUR- CURED RUBBER VULCANIZATES Henry J. Leibu, New Castle, Del., assignor to E. I. du

Pont de Nemours and Company, Wilmington, Del.,

a corporation of Delaware Filed July 30, 1968. Published May 6, 1969 Int. Cl. B32b 25/02; C08g 51/60; C08d 13/28 U.S. Cl. 260--873 No Drawing. 30 Pages Specification Polyester fiber (yarn, cord, or fabric) in sulfur cured rubber articles (e.g., V-belts, hose, tires) is stabilized against degradation associated with certain vulcanization accelerators (thiuram sulfides, dithiocarbamates, and certain sulfenamides), by conducting the curing in the presence of 0.5-8 parts, preferably 2-5 parts, of a polycarbodiimide or mixtures thereof (per 100 parts of the rubber).

Aromatic polycarbodiimides are preferred, especially when urethane or monocarbodiimide-terminated; a representative one, made from toluene, 2,4- and 2,6-diisocyanate (80/ 20 mixture), has a molecular weight of 800. Aliphatic, cycloaliphatic, and aromatic-aliphatic polycarbodiimides are also useful.

The deleterious sulfenamides have the formula G-X, where G is 2-thiazolin-2-ylthioor 2-benzothiazolylthioand X is (optionally alkyl substituted) where R and R can be alkyl or cycloalkyl; R can also be hydrogen; prefenably R and R are C -C alkyl.

Any sulfur curable rubber can be employed. Ethylene/ propylene/non-conjugated diene copolymers (EPDM) are particularly important; other rubbers include natural rubber, synthetic polyisoprene, polybutadiene, and isobutylene-isoprene and styrene-butadiene rubber.

Conventional compounding and shaping methods and conventional rubber addends can be used, 

